fix galera.galera_sst_mysqldump test to work:
* must connect to 127.0.0.1, where mysqld is listening
* disable wsrep_sync_wait in wsrep_sst_mysqldump, otherwise
  sst can deadlock
* allow 127.0.0.1 for bind_address and wsrep_sst_receive_address.
  (it's useful in tests, or when two nodes are on the same box,
  or when nodes are on different boxes, but the connection is
  tunelled, or whatever. Don't judge user's setup). MDEV-14070
* don't wait for client connections to die when doing
  mysqldump sst. they'll die in a due time, and if needed mysql
  will wait on locks until they do. MDEV-14069

Also don't mark it big, to make sure it's sufficiently tested